The present invention relates to a patient monitoring system.
In prior art, there are patient monitoring systems for monitoring a patient's condition using monitoring parameters defined for the patient. Typical monitoring parameters include parameters descriptive of respiration, temperatures, EKG, invasive and noninvasive blood pressure, oxygen saturation of haemoglobin and similar quantities.
Patient monitoring systems are used e.g. in connection with anaesthetic treatment in operating theatres, in recovery rooms and in intensive monitoring. Previously known systems include a system commercially available under the trademark Datex AS/3.TM. (manufactured by Instrumentarium Oy, Finland). A diagram representing this prior-art system is presented in FIGS. 1 and 2 as far as necessary for an understanding of the present invention. The system comprises a central data processing unit 1 controlling all functions of the system. Connected to it are a number of peripherals, such as a display unit 3, by means of which parameters measured from the patient can be continuously monitored in the form of curves and numeric values. Moreover, the system comprises a keyboard 2, a printer 4 and other peripherals. The system is of a modular design, comprising a number of different parameter modules 5, which can be selected for inclusion in the system assembly according to the monitoring need. Individual parameter modules are designed to measure one or more monitoring parameters.
As can be seen from FIG. 2, each parameter module comprises a preamplifier 6 for preliminary amplification of a parameter signal and an A/D converter 7 for converting the parameter signal into digital form. Each parameter module may comprise, as in the Datex AS/3.TM. system, a data processing unit 13, such as a microprocessor or the like, for the processing of a digital parameter signal and execution of tasks associated with measurement parameters, e.g. supervision of the operation of a module etc. The data processing unit may also control e.g. pneumatic components and work up the measurement results for input to the central data processing unit 1. At the same time, the central data processing unit 1 is performing higher-level tasks, such as collecting trends, taking care of various alarms and the set-up and control of a user interface. Furthermore, the system comprises a first optical transmitter-receiver 8 for isolating the data transfer of the digital parameter signal to achieve patient isolation. In this prior-art module, an optical data transfer and power supply isolation interface, achieved using a transformer, is placed on a circuit board. Further, as can be seen from FIG. 1, this prior-art system comprises data transfer equipment to allow data communication between the central data processing unit 1 and the optical first transmitter-receivers 8 of the parameter modules 5. The parameter modules are mounted on a common coupling frame 9, in which they can be locked, detached and replaced.
The system further comprises parameter sensors 10 to be connected to the patient and sensor cables 11 for each parameter sensor to pass the parameter signal from the parameter sensor to the pre-amplifier 6 of the parameter module corresponding to the parameter concerned.
For instance, in the prior-art Datex AS/3.TM. system (FIG. 1), the coupling frame 9 is a box with one side open, into which the parameter modules 5 can be inserted side by side. The back side of the module and correspondingly the coupling frame back wall, against which the back side is placed when the module is mounted, are provided with electric connectors for data transfer 28 and power supply 29, aligned with each other so that when the module is inserted into the coupling frame, the connectors 28, 29 of the module plug into corresponding connectors in the coupling frame back wall, thus connecting the data transfer central unit of the module to a data communication bus 30, 31 (module bus 30, AS/3 bus 31) and the power supply line to a voltage source 32.
A problem with the type of connection described above is that the connectors of the module and coupling frame have to be accurately located at the right positions relative to each other with very small tolerances to ensure successful simultaneous engagement of several adjacent connectors. A further problem is the large number of plug-in connectors. The connectors tend to gather impurities and are difficult to clean, which becomes a problem in an environment supposed to be sterile. Another problem in this prior-art system is that the cables from the modules to the patient must be relatively long because the prior-art coupling frame box cannot be placed near the patient. Further problems result from the long cables as adjacent cables run in a disorderly manner, hitching together into a cable mess. On the other hand, optic connectors are very expensive.